Rainy day rotors

[humfrz]

Originally Posted by remhex

I'm not trolling. I got the feeling you folks just had no idea what I'm talking about. I didn't see anyone with a similar issue. If I apply light brake pressure, brakes won't respond when soaked for a few seconds. I apply more pressure they work but not nearly as responsive as warmed up dry brakes. I'm not hard enough on my brakes to crack them. I agree that drilled rotors aren't ideal for normal use, less surface area for pads to bite on. I ended up doing some more research on some other forums and using drilled rotors isn't uncommon for wet conditions. Neither is tapping them every once in a while to keep them dry. Brembo's website specifically lists use of drilled rotors for better wet weather performance. Same with porsche and some other ones. They can't all be wrong. I figured since the performance package has larger pads and rotors, that's less psi on the disk per an amount of braking compared to non pp brakes. Sorry to anyone who got offended in internet land. I'm done with this thread so don't worry bout it.

Oh, please don't go away mad.

I always tap (pump) my brakes before I apply steady pressure.

Why?

Because, back in the day, with single cylinder brake cylinders, I got used to "pumping" the brakes to get the pressure up and to make sure they still worked.

Old habits and all that. Now, about when we had mechanical brakes, shut up, humfrz, nobody wants to hear about that -


humfrz

[churchx]

Drilled rotors mostly were thing of past, when used brake pad compounds of back then released lot of gas when overheated, which needed to escape. Drilled holes do minimal to enhancing cooling, but they do make rotors more susceptible to cracking. On track, braking you can rely on, is must. Hence i'd run from using drilled ones, which imho belong only for show cars or at most for street, with light braking. In terms of reliability, blanks > slotted > drilled > slotted and drilled. About the only change that one may find positive from non blanks, a bit different pad bite due more leading edge on rotor surface. Not much weight to be saved, not much cooling to be gained. At least not enough to justify reduction to reliability. I'd probably won't go futher then using quality slotted rotors.
As for wet trackdays in rain .. been at such too, see it no way as justifying reason for rotor swap to drilled ones. Braking was fine everywhere. If any water splashes .. never felt any impact from that, probably because water evaporates almost right away from hot brakes. Only (short/initial braking) time i felt a bit impact from water on braking was when i pressure washed car, including wheels/brakes to clean of brake dust, and slowly drove off. Again few sec with pressed brakes while driving, "fixed that". If anything, imho splashed water on gloving hot drilled rotors, may potentially even further increase chance for them to crack, due quick thermal expansion/shrinking.

[ls1ac]

Back several years I was doing telemetry for a turn left team. Much testing for best rotor and pads. Nothing to show advantage of either slots or holes.
That said the op had to be talking about street use. Testing for street is usually seat of the pants, No way to replicate all conditions, so anything is possible. Or it is in a lab by some manufacturer, ie slanted.
Humfrz I too have the old habit on the street, just incase we had nothing there. I also think it may be related to old drum brakes with out auto adjusters. A long push to get them to grab, too lazy to get under to adjust them in the rain.

[remhex]

I ended up ordering a set of DBA rotors. I've steered clear of any rotors with holes or slots for years for same reasons as you are advising against them. Less surface area, chance of cracking, and because they look like a ricey gimmick (no offense if you have em.) I'm not racing on these brakes, just enjoying my local roads. When I say they don't respond when its wet, I really mean it. Sometimes its not multiple seconds but depending on the situation, even a 1/2 second can scare the crap out of me. Enough so that I tap them every once in a while when its raining out as a pre-emptive measure or start braking early to dry them off. If it was just corners or stop signs to worry about, I would leave them as-is. Wildlife is my major concern. I've seen bears, a few deer, 1 moose (basically a big-foot sighting where I'm at.) But the worst for me are porcupines both dead and alive. I want my brakes to work immediately when I need them. There's more rain than sun here. There's not many spots of large areas of standing water but tons of little pools from frost heaves, potholes, and the lengthwise "ruts" from other cars. I hope they work. I doubt that having holes to allow steam to escape or a non-flat surface that should break up the water film will hurt performance too much.

[x808drifter]

New pads and turned or new rotors.

Bed them in correctly.

Flush brake fluid too.

[86MLR]

I've tapped my brakes just before my braking point, just prior to T1 at Eastern Creek, fastest corner at the track, I went through one time and when I hit the brakes, nothing happened, I almost crashed bad, from that little trip I always make sure I have pedal before I really, really need it.

[ZDan]

Originally Posted by remhex

I'm not trolling. I got the feeling you folks just had no idea what I'm talking about. I didn't see anyone with a similar issue. If I apply light brake pressure, brakes won't respond when soaked for a few seconds. I apply more pressure they work but not nearly as responsive as warmed up dry brakes.

My theory:
It's the PP Brembos… They're great, but the the fixed caliper holds the pads nearly perfectly parallel with rotors at all times. When there's a lot of water, there becomes a thin uniform film between pads and rotors that isn't easily displaced with pressure. You press on the brake pedal and get very little response for a very short but very noticeable amount of time.

Sliding calipers will have the pads a bit cocked relative to the rotors, so there's a wedge of water that is easily immediately squeezed out with pressure applied.

I got this phenomenon in a big way on my FD with ST40 Stoptechs. And now I get it with my BRZ PP. Particularly when exiting the carwash! Rotors have to be "cleared" of water before the brakes operate normally.

Very noticeable, very real phenomenon.

[remhex]

Whew..So I'm not the only one. Thanks Zdan.

[Tristor]

I'm not sure why you insisted on ignoring my excellent advice which directly addressed your question. I wasn't trolling. You should investigate different pad compounds. The pad compound that came with your PP Brembos may not be adequate for your purposes. Simple as that. For a primarily street driven car you might start looking at something like the Carbotech 1521 or the EBC RedStuff. There's a large breadth of different compounds which are more aggressive but streetable you could try.

[remhex]

I'm not convinced that a different compound would clear the water off any faster. The brakes are outstanding when dry. I may eventually do pads as well but I'm pretty convinced that drilled rotors will make more of a difference. Thank you for your input.

[ZDan]

Originally Posted by Tristor

I'm not sure why you insisted on ignoring my excellent advice which directly addressed your question. I wasn't trolling. You should investigate different pad compounds. The pad compound that came with your PP Brembos may not be adequate for your purposes. Simple as that. For a primarily street driven car you might start looking at something like the Carbotech 1521 or the EBC RedStuff. There's a large breadth of different compounds which are more aggressive but streetable you could try.

For a street-driven car, the factory pads are fine. Any pad would exhibit the same behavior, as I'm pretty sure it's down a thin uniform layer of water between pads and rotor. Pad compound shouldn't matter at all in that case.

[remhex]

I bought it new. 5800 miles on it.

[wparsons]

Originally Posted by ZDan

My theory:
It's the PP Brembos… They're great, but the the fixed caliper holds the pads nearly perfectly parallel with rotors at all times. When there's a lot of water, there becomes a thin uniform film between pads and rotors that isn't easily displaced with pressure. You press on the brake pedal and get very little response for a very short but very noticeable amount of time.

Sliding calipers will have the pads a bit cocked relative to the rotors, so there's a wedge of water that is easily immediately squeezed out with pressure applied.

I got this phenomenon in a big way on my FD with ST40 Stoptechs. And now I get it with my BRZ PP. Particularly when exiting the carwash! Rotors have to be "cleared" of water before the brakes operate normally.

Very noticeable, very real phenomenon.

I'm about 95% positive that the PP Brembo's have a slight bias on the pistons so that the leading edge engages first. That's one of the reasons the STI Brembo's weren't suggested as a good option, when you flip them so the bleeder is on the top the piston stagger is backwards.

[NoHaveMSG]

Originally Posted by ZDan

My theory:
It's the PP Brembos… They're great, but the the fixed caliper holds the pads nearly perfectly parallel with rotors at all times. When there's a lot of water, there becomes a thin uniform film between pads and rotors that isn't easily displaced with pressure. You press on the brake pedal and get very little response for a very short but very noticeable amount of time.

Sliding calipers will have the pads a bit cocked relative to the rotors, so there's a wedge of water that is easily immediately squeezed out with pressure applied.

I got this phenomenon in a big way on my FD with ST40 Stoptechs. And now I get it with my BRZ PP. Particularly when exiting the carwash! Rotors have to be "cleared" of water before the brakes operate normally.

Very noticeable, very real phenomenon.

I have ST40 Stoptechs and don't notice it I couldn't imagine any significant amount of water clinging to the rotor as it spinamathings around at high RPM.

I used to trail the brakes on my toyota after a water crossing, but that was due to having drum brakes.